It is now well established that neuronal activity produces transient changes in the expression of a number of immediate-early genes, such as zif268 and c-fos. Previous studies have shown that immunodetection for their products may be used to label activated neurons under conditions of selective stimulation. We have determining if the different time course of mRNA and protein induction, approximately 30 m and 2 h after onset of stimulation, may be used to visualize neurons that are separately activated under different stimulus conditions, thus allowing double labeling strategies. We are using immunostaining to detect the Zif268 protein and in situ hybridization histochemistry (ISHH) to detect zif268 mRNA in striate cortex of adult vervet monkeys following a reverse-occlusion procedure to map occular dominance columns.